Storage control system and power consumption control method

ABSTRACT

A storage control system acquires, for each of a plurality of power control groups in which a plurality of storage devices which form the basis of a plurality of redundancy configuration groups are classified, an I/O (Input/Output) amount of the power control group. For each of the plurality of power control groups, the storage control system controls power consumption of each of the storage devices belonging to the power control group in power control group units, based on the acquired I/O amount relating to the power control group. None of the plurality of redundancy configuration groups spans two or more power control groups among the plurality of power control groups, all being contained in any of the plurality of power control groups.

CROSS-REFERENCE TO PRIOR APPLICATION

This application relates to and claims the benefit of priority fromJapanese Patent Application number 2018-113170, filed on Jun. 13, 2018the entire disclosure of which is incorporated herein by reference.

BACKGROUND

The present invention generally relates to storage control of aplurality of storage devices and more particularly to power consumptioncontrol.

As technology relating to power consumption control of a plurality ofstorage devices, the technology disclosed in PTL 1, for example, isknown. According to PTL 1, power consumption control is performed in HDD(Hard Disk Drive) units or in RAID (Redundant Array of Independent (orInexpensive) Disks) group units.

-   [PTL 1] Japanese Patent Application Laid-Open Publication No.    2013-097635

SUMMARY

In recent years, the storage capacity of storage device units has beenincreasing and at least one storage device sometimes belongs to aplurality of RAID groups. In such a case, when power consumption iscontrolled in HDD units or RAID group units, I/O performance drops andconsequently there is a risk that the balance between I/O performanceand power savings will be adversely affected. More specifically, forexample, the power consumption of the HDD or RAID group is reduced dueto the fact that the I/O amount (I/O frequency, for example) of acertain HDD or RAID group is small. However, when this HDD or at leastone HDD which belongs to the RAID group belongs to a RAID group with alarge I/O amount, the I/O performance of the large I/O amount RAID groupcan drop.

This kind of problem can also arise in a case where another type ofredundancy configuration group (a RAIN (Redundant Array of Independent(or Inexpensive) Nodes), for example) is adopted instead of or inaddition to the RAID group.

The storage control system acquires, for each of a plurality of powercontrol groups in which a plurality of storage devices which form thebasis of a plurality of redundancy configuration groups are classified,an I/O (Input/Output) amount of the power control group. For each of theplurality of power control groups, the storage control system controlspower consumption of each of the storage devices belonging to the powercontrol group in power control group units, based on the acquired I/Oamount relating to the power control group. None of the plurality ofredundancy configuration groups spans two or more power control groupsamong the plurality of power control groups.

According to the present invention, even when at least one of thestorage devices belongs to a plurality of redundancy configurationgroups, the balance between I/O performance and power savings can bemaintained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic overview of a first embodiment.

FIG. 2 shows a configuration of a whole system comprising a storagesystem.

FIG. 3 shows a configuration of a PSNG management table.

FIG. 4 shows a configuration of an I/O performance requirement table.

FIG. 5 shows a configuration of a mapping table.

FIG. 6 shows a configuration of a power management table.

FIG. 7 shows power characteristics of a certain NVRAM.

FIG. 8 shows the flow of PSNG construction processing.

FIG. 9 shows the flow of overall power consumption control.

FIG. 10 shows the flow of power consumption control for a target PSNG.

FIG. 11 shows the flow of processing to increase the level of the targetPSNG.

FIG. 12 shows the flow of processing to reduce the level of the targetPSNG.

FIG. 13 shows a configuration of a mapping table according to a secondembodiment.

DESCRIPTION OF EMBODIMENTS

In the ensuing explanation, ‘interface unit’ may refer to one or moreinterfaces. The one or more interfaces may be one or more communicationinterface devices of the same type (for instance, one or more NIC(Network Interface Cards)) or may be two or more communication interfacedevices of different types (for instance, an NIC and an HBA (Host BusAdapter)).

Furthermore, in the ensuing explanation, ‘memory unit’ may be one ormore memories and may, typically, be a main storage device.

Furthermore, in the ensuing explanation, ‘PDEV unit’ may be one or morePDEV and may, typically, be an auxiliary storage device. ‘PDEV’ is anexample of a storage device and in particular signifies a physicalstorage device (Physical storage DEVice) and is typically a nonvolatilestorage device.

Furthermore, in the ensuing explanation, ‘storage unit’ is at least oneof a memory unit and at least a portion of a PDEV unit (typically, atleast a memory unit).

Furthermore, in the ensuing explanation, ‘processor unit’ is one or moreprocessors. At least one processor is typically a microprocessor like aCPU (Central Processing Unit) but could also be another type ofprocessor such as a GPU (Graphics Processing Unit). At least oneprocessor could also be a single-core or multi-core processor. At leastone processor could also be a processor in a broader sense such as ahardware circuit which performs some or all of the processing (an FPGB(Field-Programmable Gate Array) or ASIC (Application Specific IntegratedCircuit), for example).

Moreover, although information for which an output is obtained inresponse to an input is explained in the ensuing explanation by usingexpressions such as ‘xxx table,’ information of this type could also bedata of any structure or could be a learning model such as a neuralnetwork which generates an output in response to an input. Therefore,‘xxx table’ can be referred to as ‘xxx information.’ Moreover, in theensuring explanation, the configuration of each table is an example, andone table could also be divided into two or more tables, or all or aportion of two or more tables could also be one table.

Furthermore, in the ensuing explanation, although functions aresometimes explained using an expression ‘kkk unit’ (excluding interfaceunits, storage units and processor units), the functions could berealized as a result of one or more computer programs being executed bya processor unit or could be realized by one or more hardware circuits(for example, an FPGA (Field-Programmable Gate Array) or an ASIC(Application Specific Integrated Circuit)). When the functions arerealized as a result of programs being executed by a processor unit,determined processing is performed while suitably using a storage unitand/or an interface unit, and the like, and hence the functions may beimplemented by at least a portion of a processor unit. Processing whichis explained with the function serving as the subject of the sentencemay be processing that is performed by a processor unit or by anapparatus which comprises a processor unit. A program could also beinstalled from a program source. A program source could also be aprogram distribution computer or a computer-readable recording medium(for example, a non-transient recording medium). The explanation of eachfunction is an example, and a plurality of functions could also begathered as one function or one function could also be divided into aplurality of functions.

Furthermore, in the ensuing explanation, ‘redundancy configurationgroup’ is a storage device group which is configured from two or morestorage devices and which stores redundant data. Redundancyconfiguration examples include Erasure Coding, RAIN (Redundant Array ofIndependent Nodes), internode mirroring, RAID (Redundant Array ofIndependent (or Inexpensive) Disks) and so forth, and any redundancyconfiguration may be adopted. Therefore, ‘storage device’ may be astorage medium such as an NVRAM (Non-Volatile RAM) or may be a nodewhich is a constituent element of a scale-out-type storage system (ageneral-purpose computer, for example). Furthermore, a ‘storage system’may be a storage system which comprises a plurality of storage media asthe plurality of storage devices or may be a storage system whichcomprises a plurality of nodes as the plurality of storage devices (ascatter storage system, for example). In the embodiments hereinbelow,the storage system is the former storage system, and the storage controlsystem for the former storage system may be a controller in the storagesystem. For the latter storage system, the storage control system may bea processor unit which executes a predetermined program in each node.More specifically, for example, the ‘storage system’ may be a systemwhich comprises one or more physical computers. A physical computer maybe a general-purpose computer or a dedicated computer. In at least onephysical computer, one or more virtual computers (VM (Virtual Machines),for example) may be executed. A virtual computer may be a computer whichissues I/O requests or a computer which performs data I/O in response toI/O requests. As a result of a physical computer executing predeterminedsoftware, SDx (Software-Defined anything) may be constructed in thephysical computer or in a system which comprises this physical computer.As SDx, SDS (Software Defined Storage) or SDDC (Software-definedDatacenter), for example, can be adopted. For example, an SDS storagesystem may be constructed as a result of software which comprises astorage function being executed by a physical, general-purpose computer.Furthermore, at least one physical computer (storage server, forexample) may execute one or more virtual computers as a host computerand a virtual computer as a storage control system of the storage system(typically, an apparatus which inputs and outputs data to the PDEV unitin response to an I/O request). In other words, at least one physicalcomputer may comprise both a function serving as at least a portion ofthe host computer and a function serving as at least a portion of thestorage system.

Furthermore, in the ensuing explanation, when elements of the same typeare explained without distinction, reference signs are used and whenelements of the same type are explained with a distinction being made,element IDs are sometimes used. For example, when the NVRAM areexplained without a particular distinction being made, same appear as‘NVRAM 110’ and when the explanation makes a distinction betweenindividual NVRAM, same sometimes appear as ‘NVRAM1,’ “NVRAM2,’ and soforth. Note that, in the ensuing explanation, the reference signs are of3 or more digits and the IDs are of less than 3 digits.

Several embodiments will be explained hereinbelow.

First Embodiment

FIG. 1 shows a schematic overview of a first embodiment.

A storage system 100 comprises a plurality of NVRAM 110 and a storagecontrol system 101 which controls data I/O (Input/Output) to/from theplurality of NVRAM 110. The NVRAM 110 is a device which has anonvolatile semiconductor memory. The storage may be flash memory, PRAM(Phase-change Random Access Memory), MRAM (Magnetoresistive RandomAccess Memory), ReRAM (Resistive Random Access Memory) or FeRAM(Ferroelectric Random Access Memory).

The storage control system 101 creates a high order NVRAM group 130 in aRAID group (redundancy configuration group) 120 according to aninstruction from a management PC, described subsequently, or apreconfigured policy. The high order NVRAM group 130 is an example of apower control group. The high order NRAM group 130 will hereinafter becalled the PSNG (Power Saving NVRAM Group) 130. The storage controlsystem 101 performs power consumption control of the NVRAM 110 in PSNGunits). Any RAID group 120 is also included in any PSNG 130. In otherwords, no RAID group 120 spans two or more PSNG 130. That is, all theNVRAM 110 which belong to one RAID group 120 are included in any onePSNG 130 and do not span two or more PSNG 130. More specifically, forexample, as shown in the drawings, one NVRAM 110 (each of NVRAM3 toNVRAM5) can belong to a plurality of RAID groups 120 (RAID groups 1 and2) but any given RAID group 110 does not span two or more PSNG 130.

The storage control system 101 comprises an I/O amount acquisition unit141 and a power control unit 142.

The I/O amount acquisition unit 141 acquires the I/O amount for each ofthe plurality of PSNG 130. The I/O amount may be acquired at regular orirregular intervals. The I/O amounts acquired may be I/O amounts whichare measured by the I/O amount acquisition unit 141 (or by a separatesystem from the storage control system 101). At least one of an ‘I/Ocount’ and ‘I/O size’ can be adopted as the ‘I/O amount.’ The ‘I/Ocount’ is the number of I/O commands (for example, the number of I/Ocommands per unit of time (that is, an I/O frequency such as IOPS)). The‘I/O size’ is the size of the I/O target data (for example, the size ofthe data which is input/output per unit of time (an I/O throughput suchas the transfer speed)). For each PSNG 130, the I/O amount of the PSNG130 is an I/O amount according to the I/O amount of all the NVRAM 110which belong to the PSNG 130 (the total or average, for example).

The power control unit 142 controls, for each of the plurality of PSNG130, the power consumption of each of the NVRAM 110 belonging to thePSNG 130 in PSNG units based on the acquired I/O amount relating to thisPSNG 130.

As a result, even when at least one NVRAM 110 belongs to a plurality ofRAID groups 120, the balance between I/O performance and power savingscan be maintained.

As levels of power savings in PSNG units, power saving levels of aplurality of stages are provided. For example, at least one of thefollowing may differ depending on the PSNG 130 or may be common to allthe PSNG 130:

-   -   the number of power saving levels (number of stages).    -   the value of power saving levels. For example, ‘Normal,’        ‘Level1,’ and ‘Level2,’ as illustrated in the drawings. In this        embodiment, ‘Normal’ is the lowest power saving level (weak        power savings, that is, high power consumption), and the higher        the numerical value of a in ‘Levela’ is, the higher the power        saving level (strong power savings, that is, low power        consumption).    -   the I/O performance requirements for each power saving level.        More specifically, for each power saving level, the I/O        performance that is required in the power savings state        according to the power saving level. The I/O performance        requirements can also be represented as the I/O amount threshold        range. In other words, like the ‘I/O amount,’ the ‘I/O        performance’ is represented by at least one of the ‘I/O count’        and the ‘I/O size.’

I/O performance requirements (upper limit and lower limit thresholds ofthe I/O amount) are associated with each power saving level. The I/Operformance requirements are configured manually by the user, forexample (the system administrator, for example) but could also beconfigured automatically based on a predetermined policy. The powercontrol unit 142 performs the following (a) to (d) for each PSNG 130:

(a) The power control unit 142 determines whether or not the I/O amountacquired for the PSNG 130 satisfies the I/O performance requirements(I/O amount threshold range) which correspond to the current powersaving level of the PSNG 130.

(b) When the determination result of (a) is true, the power control unit142 maintains the power saving level of the PSNG 130 at the currentpower saving level (see, for example, Case1 and Case2 for PSNG1).

(c) When the determination result of (a) is false and the I/O amount ofthe PSNG 130 is less than the lower limit threshold which corresponds tothe current power saving level of the PSNG 130, the power control unit142 increases the current power saving level (see Case3 for PSNG2 andCases 5 and 6 for PSNG3, for example).

(d) When the determination result of (a) is false and the I/O amount ofthe PSNG 130 is equal to or larger than the upper limit threshold whichcorresponds to the current power saving level of the PSNG 130, the powercontrol unit 142 reduces the current power saving level, that is,weakens the power savings (see Case4 for PSNG2, for example).

As a result of the foregoing processing, the configured power savinglevel is maintained at the power saving level suited to the acquired I/Oamount, for each of the PSNG 110. The specific details are as follows.That is, if the change in the I/O amount remains small, the power savinglevel is not modified (see Case1 and Case2). If the I/O amount increasesafter being reduced, the power saving level is reduced after beingraised (see Case3 and Case4). If the I/O amount is reduced further afterbeing reduced, the power saving level is raised further after beingraised (see Case5 and Case6). Note that the configured power savinglevel (current power saving level) may be modified one level at a timeirrespective of the relationship between the acquired I/O amount and I/Operformance requirements or may be modified to the power saving levelwhich corresponds to the I/O performance requirements which the acquiredI/O amount satisfies.

The power savings function of the NVRAM 110 is used to control the powerof the PSNG 130. The NVRAM 110 is an example of a storage device whichis also capable of transitioning to any power savings state of aplurality of stages which are I/O-capable states (any of the powersaving levels of the plurality of I/O-capable stages can be configured).More specifically, for example, the NVRAM 110 has power saving levels ofa plurality of stages. To avoid confusion, the power saving levels forthe PSNG 130 will be called ‘PSNG power saving levels’ and the powersaving levels for the NVRAM 110 will be called ‘NVRAM power savinglevels’ hereinbelow. As the NVRAM power saving levels, ‘N’ (Normal),‘Lv1,’ and ‘Lv2’ are illustrated in FIG. 1. The larger the numericalvalue of β in ‘Lvβ’ is, the higher the power saving level (the strongerthe power savings, that is, the smaller the power consumption). The I/Operformance of the NVRAM 110 varies depending on the NVRAM power savinglevel. At least a portion of the plurality of NVRAM 110 comprises two ormore NVRAM 110 with a different power characteristic (the relationshipbetween I/O performance and power consumption). More specifically, forexample, the power characteristic of the NVRAM 110 is differentdepending on the NVRAM 110 (or depending on the type such as the typename of the NVRAM 110 or the like). Therefore, in this embodiment, foreach NVRAM 110, the NVRAM power saving level, among NVRAM power savinglevels of a plurality of stages, which corresponds to the NVRAM 110, isassociated with each PSNG power saving level. In the power consumptioncontrol in PSNG units, for each PSNG 130, the NVRAM power saving levelof each NVRAM 110 which belongs to the PSNG 130 is taken as the NVRAMpower saving level which is associated with the current power savinglevel of the PSNG 130. For this reason, within one PSNG 130, a variationin the values of the configured NVRAM power saving levels can arise (seeCase6). Even when there is a mixture of NVRAM 110 with different powercharacteristics in one PSNG 130, an average (uniformity) in the I/Operformance of all NVRAM 110 can be expected in this one PSNG 130. Notethat the configuration of the NVRAM power saving levels involvesconfiguring designated values according to the NVRAM power saving levelsin a power savings configuration register, described subsequently, ofthe NVRAM 110. The NVRAM 110 controls the power consumption of the NVRAM110 according to the designated values thus configured. The designatedvalues are equivalent to the NVRAM power saving levels. Accordingly,associating the NVRAM power saving levels with the PSNG power savinglevels is equivalent to associating the designated values with the PSNGpower saving levels. In other words, the designated values for the NVRAM110 are associated with the PSNG power saving levels regardless ofwhether or not NVRAM power saving levels exist.

The power control unit 142 adjusts the power saving levels between thePSNG 130 in order to keep the overall power consumption at or below apower capping value (an upper limit for the overall power consumption).More specifically, for example, when reducing the power saving level ofa first PSNG 130, the power control unit 142 determines whether or notthe estimated overall power consumption in a case where a reduction inthe power saving level of this certain PSNG 130 is assumed, exceeds thepower capping value. The ‘overall power savings’ is the powerconsumption for a whole entity (the storage system 100, for example)which comprises the plurality of NVRAM 110. If the result of thisdetermination is true, the power control unit 142 keeps the estimatedoverall power consumption at or below the power capping value byincreasing the power saving level of a second PSNS 130. The ‘secondPSNG’ is a PSNG of a lower QoS (Quality of Service) priority (priorityexample) than the first PSNG. As a result, the balance between I/Operformance and power savings can be maintained while satisfying QoSpriorities. Note that the power capping value may be configured(modified) by the user (administrator, for example) via processing PCwhich will be described subsequently.

This embodiment will be explained in detail hereinbelow.

FIG. 2 shows a configuration of the whole system which comprises thestorage system.

The storage system 100, a host server 260 and a management PC (PersonalComputer) 270 are coupled to a network 280. The host server 260 is anexample of a host computer and issues an I/O request to volumes (addressspace) provided by the storage system 100. The management PC 270 is anexample of a management computer and manages the storage system 100. Theuser (typically, the administrator) is able to perform configuration ofthe PSNG 130, configuration of the RAID groups 120, and configuration ofthe power capping value for the storage control system 101 via themanagement PC 270 (or host server 260). The network 280 may be one ormore networks which are configured from a fibre channel, ethernet(registered trademark) Infiniband or LAN (Local Area Network) or thelike.

The storage system 100 comprises a plurality of NVRAM 110, a storagecontrol system 101 which controls I/O to/from the plurality of NVRAM110, and a power supply apparatus 250 which supplies various hardwareresources in the storage system 100 by changing a commercial powersupply (AC power supply) to a DC power supply. The power supplyapparatus 250 comprises a power supply monitor unit 251 which measuresthe overall power consumption.

The NVRAM 110 each comprise a power savings configuration register 220which is a register in which designated values for power consumptioncontrol are configured. The NVRAM 110 each perform power consumptioncontrol of the NVRAM 110 according to designated values which have beenconfigured in the power savings configuration register 220 of the NVRAM110.

The storage control system 101 is a redundant storage controller 210,for example. The storage controller 210 comprises an FE (Front-end)interface 211, a BE (Back-end) interface 212, a memory 213, and a CPU214 which is coupled to the FE interface 211, BE interface 212, andmemory 213. The FE interface 211 and BE interface 212 are examples ofinterface units. The memory 213 is an example of a memory unit. The CPU214 is an example of a processor unit.

The FE interface 211 is coupled to the network 280 and is an interfacedevice for communicating with external apparatuses (the host server 260and management PC 270) of the storage system 100. The BE interface 212is an interface device for communicating with the NVRAM 110.

The memory 213 may be configured from volatile semiconductor memory suchas SRAM (Static RAM (Random Access Memory)) or DRAM (Dynamic RAM) andthe like. The memory 213 stores a plurality of programs including acontrol program 291, and a table group 292 which is one or more tables(an example of management information). The table group 292 includes aPSNG management table, an I/O performance requirement table, a mappingtable, and a power management table which will be describedsubsequently.

The CPU 214 administers operational control of the whole storagecontroller 210 by executing a program in the memory 213. For example, asa result of the CPU 214 executing the control program 291, functionssuch as an I/O control unit 295, the I/O amount acquisition unit 141,the power control unit 142, a configuration management unit 296, and apower monitor unit 297 are realized. The I/O control unit 295 controlsI/O to/from the NVRAM 110 according to I/O requests from the host server260 (or in predetermined internal processing). The I/O amountacquisition unit 141 and power control unit 142 are as described above.The configuration management unit 296 performs configuration of the PSNG130 and so forth. The power monitor unit 297 acquires the overall powerconsumption from the power supply monitor unit 251 of the power supplyapparatus 250.

The PSNG management table, I/O performance requirement table, mappingtable, and power management table which are contained in the table group292 will be explained hereinbelow.

FIG. 3 shows a configuration of the PSNG management table.

A PSNG management table 300 holds information relating to theconfiguration of each PSNG 130. More specifically, for example, the PSNGmanagement table 300 comprises an entry for each NVRAM 110. Each entrystores information such as a PSNG#301, PSNG power saving levels 302, aQoS 303, an NVRAM#304, an RG#305, a start address 306 and a capacity307. The PSNG power saving levels 302 include a current level 311, alower limit 312, and an upper limit 313. One NVRAM 110 is taken as anexample hereinbelow (the ‘target NVRAM 110’ in the explanation of FIG.3).

The PSNG#301 indicates the ID (identification number, for example) ofthe PSNG 130 which comprises the target NVRAM 110. In the explanation ofFIG. 3, the PSNG 130 which comprises the target NVRAM 110 is called the‘target PSNG 130.’ The current level 311 indicates the current PSNGpower saving level which has been configured for the target PSNG 130.The lower limit 312 indicates the lower limit among the PSNG powersaving levels which can be configured for the target PSNG 130. The upperlimit 313 indicates the upper limit among the PSNG power saving levelswhich can be configured for the target PSNG 130. QoS 303 indicates theQoS priority which has been configured for the target PSNG 130. TheNVRAM#304 indicates the ID of the target NVRAM 110. The RG#305 indicatesthe ID of the RAID group 120 which comprises the target NVRAM 110. Inthe explanation of FIG. 3, the RAID group 120 which comprises the targetNVRAM 110 is called the ‘target RG 120.’ The start address 306 indicatesthe initial address of the logical address space which is provided bythe target NVRAM 110 among the logical address spaces provided by thetarget RG 120. The capacity 307 indicates the storage capacity of thetarget NVRAM 110.

In this embodiment, the smaller the value of QoS 303 is, the higher theQoS priority (that is, ‘1st’ is the highest QoS priority).

FIG. 4 shows a configuration of an I/O performance requirement table.

An I/O performance requirement table 400 holds information relating toI/O performance requirements. More specifically, for example, the I/Operformance requirement table 400 comprises an entry for every PSNGpower saving level of each PSNG 130. Each entry holds information suchas a PSNG#401, power saving level 402, and I/O performance requirements403. The I/O performance requirements 403 include an upper limit 411 anda lower limit 412. One power saving level of one PSNG 130 will be takenas an example hereinbelow (called the ‘target PSNG 130’ and ‘target PSNGpower saving level’ in the explanation of FIG. 4).

The PSNG#401 is the ID of the target PSNG 130. The power saving level402 indicates the power saving level of the target PSNG. The upper limit411 indicates the upper limit among the I/O performance requirements (inthe I/O amount threshold range) which corresponds to the power savinglevel of the target PSNG. The lower limit 412 indicates the lower limitamong the I/O performance requirements which corresponds to the powersaving level of the target PSNG.

The I/O amount threshold is both the I/O count and the I/O size per unitof time (one minute, for example). When the I/O amount acquired for thetarget PSNG 130 is equal to or larger than the upper limit 411 or lessthan the lower limit 412, both (or one of) the I/O count and the I/Osize per unit of time which are the I/O amounts acquired for the targetPSNG 130 are (is) equal to or larger than the upper limit 411 or lessthan the lower limit 412.

Note that the PSNG power saving levels of a plurality of stages couldalso be common to all the PSNG 130.

FIG. 5 shows a configuration of a mapping table.

A mapping table 500 holds information indicating the mappingrelationships between the PSNG power saving levels of the PSNG 130 andthe NVRAM power saving levels of each NVRAM 110 which belongs to thePSNG 130. If the number of stages of the PSNG power saving levels andI/O performance requirements and so forth are different for every PSNG130, the mapping table 500 may be prepared for every PSNG 130, and ifthe number of stages of the PSNG power saving levels and the I/Operformance requirements and so forth are common to all the PSNG 130,the mapping table 500 may be common to all the PSNG 130.

One PSNG 130 is taken as an example (the ‘target PSNG 130’ in theexplanation of FIG. 5). In the mapping table 500, specifically, forexample, for each NVRAM (or NVRAM type) which belongs to the target PSNG130, the NVRAM power saving level, among the NVRAM power saving levelsof a plurality of stages, which corresponds to this NVRAM 110 isassociated with each of the power saving levels of a plurality of stagesof the target PSNG 130. When one PSNG power saving level and one NVRAM110 are taken as an example, the ‘the NVRAM power saving level’ is thehighest NVRAM power saving level (that is, with the strongest powersavings) among the NVRAM power saving levels which enable the NVRAM 110to demonstrate the I/O performance corresponding to the PSNG powersaving level (for example, the I/O performance indicated by the‘performance index’ illustrated in FIG. 5 for the PSNG power savinglevel). For this reason, when two or more NVRAM 110 of different powercharacteristics are mixed in the target PSNG 130, the NVRAM power savinglevels which are associated with the same PSNG power saving level aredifferent for these two or more NVRAM 110. According to the example ofFIG. 5, although the NVRAM power saving level ‘LV2’ has been associatedfor NVRAM1 with the PSNG power saving level ‘Level2,’ for the NVRAM3,the power saving level ‘LV1,’ which is different from the power savinglevel of the NVRAM1, has been associated with the PSNG power savinglevel ‘Level2.’ Note that for each of the PSNG power saving levels, the‘performance index’ shown in FIG. 5 could also be an I/O performancerequirement which corresponds to the PSNG power saving level.

The mapping table 500 also holds information which indicates thedemonstrable I/O performance (write performance and read performance)and power consumption for each of the NVRAM power saving levels of eachNVRAM 110.

The mapping table 500 may be prepared as follows, for example. That is,the configuration management unit 296 scans the power characteristic(relationship between the I/O performance and power consumption) fromthe NVRAM 110, for each NVRAM 110, and may create the mapping table 500based on the information scanned from each NVRAM 110. Alternatively, thepower characteristic is embedded in code as a dictionary for varioustype names of the NVRAM 110 when coding the control program 291, and theconfiguration management unit 296 may create the mapping table 500 byscanning type names when identifying the NVRAM 110 and extracting thetype names using the dictionary as a key.

FIG. 6 shows a configuration of a power management table.

A power management table 600 holds a current value which is a valueindicating the current overall power consumption and a power cappingvalue. The current value is acquired from the power supply apparatus 250by the power monitor unit 297 at regular or irregular intervals andregistered in the power management table 600. The power capping value isinput by the user via the management PC 270 (or host server 260) andregistered in the power management table 600 by the configurationmanagement unit 296.

FIG. 7 shows the power characteristic of a certain NVRAM 110.

As shown in FIG. 7, the power consumption and I/O performance vary foreach of the NVRAM power saving levels of a plurality of stages.Moreover, there are designated values which are configured in the powersavings configuration register 220 for each of the NVRAM power savinglevels of a plurality of stages. Note that, for the same NVRAM 110, twoor more NVRAM power saving levels are each power saving levels which areI/O capable even in a power savings state. The relationships between thepower characteristics and the NVRAM power saving levels and designatedvalues which are illustrated in FIG. 7 are configured for the NVRAM 110but could also be stored as a table in the memory 213 of the storagecontroller 210.

An example of the processing performed in this embodiment will beexplained hereinbelow.

FIG. 8 shows the flow of PSNG construction processing.

The configuration management unit 296 acquires (scans) the informationindicating the type name and power characteristic from each of the NVRAM110 and creates the mapping table 500 based on this information (S801).

The configuration management unit 296 creates the PSNG 130 and registersinformation relating to the created PSNG 130 in the PSNG managementtable 300 (S802). The PSNG 130 may be created automatically based on apredetermined policy or may be created according to an instruction fromthe user.

The configuration management unit 296 registers the QoS priority andlower and upper limits for the PSNG power saving levels of each createdPSNG 130 in the PSNG management table 300 (S803). The QoS priority andlower and upper limits for the PSNG power saving levels may bedetermined automatically based on a predetermined policy or according toan instruction from the user, for each PSNG 130.

The configuration management unit 296 creates the RAID groups 120 andregisters information relating to the created RAID groups 120 in thePSNG management table 300 (S804). Thereupon, the configurationmanagement unit 296 authorizes (executes) the creation of one or moreRAID groups 120 in the PSNG 130 but prohibits (does not execute) a RAIDgroup 120 which spans two or more PSNG 130. The RAID groups 120 may becreated automatically based on a predetermined policy or may be createdaccording to an instruction from the user.

The configuration management unit 296 registers the power capping valuein the power management table 600 (S805). The power capping value may bedetermined automatically based on a predetermined policy or may conformto an instruction from the user.

FIG. 9 shows the flow of overall power consumption control.

The I/O amount acquisition unit 141 refers to the PSNG management table300 and activates power consumption control in ascending order of thevalue of QoS 303 (in order of rising QoS priority) (S901, S902, S903, .. . ).

One PSNG 130 is taken as an example and power consumption control isexplained with reference to FIGS. 10 to 12 hereinbelow (‘target PSNG130’ in the explanation of FIGS. 10 to 12).

FIG. 10 shows the flow of power consumption control for the target PSNG130.

The I/O amount acquisition unit 141 acquires the I/O amount of thetarget PSNG 130 (S1001). Note that, in this embodiment, for each PSNG130, the acquired I/O amount is the total of the I/O amounts of all theNVRAM 110 which belong to the PSNG 130. More specifically, for example,the I/O amount of each NVRAM 110 is measured (monitored) by the I/Oamount acquisition unit 141 and the I/O amount for each PSNG 130 can beacquired based on the result of this measurement.

The power control unit 142 refers to the I/O performance requirementtable 400 and determines whether or not the acquired I/O amount (Xc) isless than the lower limit 412 corresponding to the target PSNG 130(S1002).

When the determination result of S1002 is true (S1002: Yes), processing(FIG. 11) to increase the level of the target PSNG 130 is performed(S1003). This is because, at the current power saving level of thetarget PSNG 130, the acquired I/O amount is relatively small andtherefore stronger power savings are preferable.

When the determination result of S1002 is false (S1002: No), the powercontrol unit 142 refers to the I/O performance requirement table 400 anddetermines whether or not the acquired I/O amount is equal to or largerthan the upper limit 411 corresponding to the target PSNG 130 (S1004).

When the determination result of S1004 is false (S1004: No), theprocessing ends. In other words, the power control unit 142 maintainsthe current power saving level of the target PSNG 130. This is becausethe acquired I/O amount satisfies the I/O performance requirement whichcorresponds to the current power saving level for the PSNG 130.

When the determination result of S1004 is true (S1002: Yes), processing(FIG. 12) to reduce the level of the target PSNG 130 is performed(S1005). This is because, at the current power saving level of thetarget PSNG 130, the acquired I/O amount is relatively large andtherefore weaker power savings to better enable I/O performance arepreferable.

FIG. 11 shows the flow of processing to increase the level of the targetPSNG 130.

The power control unit 142 refers to the PSNG management table 300 anddetermines whether or not the current level 311 of the target PSNG 130has reached the upper limit 313 (S1101).

When the determination result of S1101 is true (S1101: Yes), theprocessing ends. In other words, the power control unit 142 maintainsthe current power saving level of the target PSNG 130. This is becausethe current power saving level of the target PSNG 130 cannot beincreased further.

When the determination result of S1101 is false (S1101: No), the powercontrol unit 142 increases the current power saving level of the targetPSNG 130 by one stage (S1102). More specifically, the power control unit142 increases the current level 311 of the target PSNG 130 by one stageand refers to the mapping table 500, and if necessary, configures thedesignated value which corresponds to the NVRAM power saving levelcorresponding to the modified current level 311 in the register 220 ofeach NVRAM 110 belonging to the target PSNG 130.

FIG. 12 shows the flow of processing to reduce the level of the targetPSNG 130.

The power control unit 142 refers to the PSNG management table 300 anddetermines whether or not the current level 311 of the target PSNG 130has reached the lower limit 312 (S1201).

When the determination result of S1201 is true (S1201: Yes), theprocessing ends. In other words, the power control unit 142 maintainsthe current power saving level of the target PSNG 130. This is becausethe current power saving level of the target PSNG 130 cannot be reducedfurther.

When the determination result of S1201 is false (S1201: No), anestimation of the overall power consumption in a case where a reductionin the current power saving level of the target PSNG 130 is assumed isperformed. More specifically, the power control unit 142 requests thatthe power monitor unit 297 estimate the overall power consumption in acase where a one-stage reduction in the current power saving level ofthe target PSNG 130 is assumed (S1202). In response to this request, thepower monitor unit 297 acquires the value of the current overall powerconsumption (for example, acquires same from the power management table600 or acquires the value of the overall power consumption recorded inthe power supply monitor unit 251 of the power supply apparatus 250),and estimates the overall power consumption in a case where a one-stagereduction in the current power saving level of the target PSNG 130 isassumed, based on this overall power consumption value and the mappingtable 500 (S1203). For example, for each NVRAM 110 which belongs to thetarget PSNG 130, the power monitor unit 297 specifies, from the mappingtable 500, the power consumption (NVRAM power consumption) whichcorresponds to the PSNG power saving level after the current PSNG powersaving level has been reduced by one stage, estimates the overall powerconsumption in a case where a one-stage reduction in the current PSNGpower saving level is assumed, based on the current overall powerconsumption value and the specified power consumption, and sends backthe overall power consumption thus estimated (estimate value) to thepower control unit 142. The power control unit 142 receives the estimatevalue from the power monitor unit 297 (S1204). Note that the estimate ofthe overall power consumption could also be performed by the powercontrol unit 142 based on the value of the current overall powerconsumption instead of by the power monitor unit 297.

The power control unit 142 refers to the power management table 600 anddetermines whether or not the estimate value (E1) obtained in S1204exceeds the power capping value (P) (S1205).

When the determination result of S1205 is false (S1205: No), the powercontrol unit 142 reduces the current power saving level of the targetPSNG 130 by one stage (S1212). More specifically, the power control unit142 reduces the current level 311 of the target PSNG 130 by one stageand refers to the mapping table 500, and if necessary, configures thedesignated value which corresponds to the NVRAM power saving levelcorresponding to the modified current level 311 in the register 220 ofeach NVRAM 110 belonging to the target PSNG 130.

If the determination result of S1205 is true (S1205: Yes), an attempt ismade to adjust the power saving level between the PSNG 130 to keep theoverall power consumption at or below the power capping value. Morespecifically, the power control unit 142 refers to the PSNG managementtable 300 and determines whether or not a PSNG 130 with a larger QoS 303(lower QoS priority) than the target PSNG 130 exists (S1206). When thedetermination result of S1206 is false (S1206: No), the processing ends.This is because power saving level adjustment between PSNG 130 wheresurplus power generated by increasing the power saving level of a PSNG130 of low QoS priority is consumed by the target PSNG 130, and soforth, is not possible.

When the determination result of S1206 is true (S1206: Yes), anestimation of the overall power consumption, in a case where a one-stageincrease in the current power saving level of the PSNG 130 with thelargest QoS 303 (the PSNG 130 with the lowest QoS priority) amongdiscovered PSNG 130 is assumed, is performed. More specifically, thepower control unit 142 requests that the power monitor unit 297 estimatethe overall power consumption in a case where a one-stage increase inthe current power saving level of a PSNG 130 with a low QoS priority anda one-stage reduction in the current power saving level of the targetPSNG 130 are assumed (S1207). In response to this request, using thesame method as S1203, the power monitor unit 297 estimates the overallpower consumption in a case where a one-stage increase in the currentpower saving level of a PSNG 130 with a low QoS priority and a one-stagereduction in the current power saving level of the target PSNG 130 areassumed (S1207). The power monitor unit 297 sends back an estimate valuewhich is the estimated overall power consumption value to the powercontrol unit 142. The power control unit 142 receives the estimate valuefor the overall power consumption from the power monitor unit 297(S1208). Note that, here, the estimate of the overall power consumptioncould also be performed by the power control unit 142 based on the valueof the current overall power consumption instead of by the power monitorunit 297.

The power control unit 142 refers to the power management table 600 anddetermines whether or not the estimate value obtained in S1208 exceedsthe power capping value (S1209). When the determination result of S1209is true (S1209: Yes) and there is not one PSNG 130 with a lower QoSpriority than the target PSNG 130, the processing ends. In other words,S1207 to S1209 are performed preferentially starting with the lowest QoSpriority as long as a PSNG 130 with a lower QoS priority than the targetPSNG 130 still exists. The processing of S1207 to S1209 is repeateduntil there are no longer any PSNG 130 with a lower QoS priority thanthe target PSNG 130.

When the determination result of S1209 is false (S1209: No), the powercontrol unit 142 increases the current power saving level (current level311) of the PSNG 130 of a low QoS priority by one stage (S1211) andreduces the current power saving level of the target PSNG 130 by onestage (S1212). In this manner, surplus power which is generated byincreasing the power saving level of a PSNG 130 of a low QoS prioritycan be consumed by the target PSNG 130, and a balance between I/Operformance and power savings can be maintained.

Second Embodiment

A second embodiment will now be explained. In so doing, points ofdifference from the first embodiment will mainly be explained, while anexplanation of points in common with the first embodiment will beomitted or simplified. One PSNG 130 is taken as an example hereinbelow(the ‘target PSNG 130’ in the explanation of the second embodiment).

FIG. 13 shows a configuration of a mapping table according to a secondembodiment.

In this embodiment, for each of the PSNG power saving levels of thetarget PSNG 130, the NVRAM power saving level for each NVRAM 110 dependson the number of RAID groups to which the NVRAM 110 belongs. Accordingto the example in FIG. 13, in the case of the PSNG power saving level‘Level1,’ if the number of RAID groups 120 to which the NVRAM1 belongsis 1 or more but less than 3, the power saving level of the NVRAM1 is‘Lv1,’ but if the number of RAID groups 120 to which the NVRAM1 belongsis 3 or more, the power saving level of the NVRAM1 is ‘Normal.’

According to the embodiment, more balance between I/O performance andpower savings can be expected.

Several embodiments were explained hereinabove but are merelyillustrations to explain the present invention, there being no intentionto limit the scope of the present invention to these embodiments alone.The present invention can also be executed in a variety of other forms.

What is claimed is:
 1. A storage control system, comprising: an I/Oamount acquisition unit which, for each of a plurality of power controlgroups in which a plurality of storage devices which form the basis of aplurality of redundancy configuration groups are classified, acquires anI/O (Input/Output) amount of the power control group; and a powercontrol unit which, for each of the plurality of power control groups,controls power consumption of each of the storage devices belonging tothe power control group in power control group units, based on theacquired I/O amount relating to the power control group, wherein theplurality of redundancy configuration groups are all a storage devicegroup which stores redundant data, and wherein none of the plurality ofredundancy configuration groups spans two or more power control groupsamong the plurality of power control groups, all being contained in anyof the plurality of power control groups.
 2. The storage control systemaccording to claim 1, wherein at least a portion of the plurality ofstorage devices is two or more storage devices for which therelationship between I/O performance and power consumption is different,wherein, for each of the plurality of power control groups, the powercontrol unit selects a power saving level which is associated with thepower control group from among power saving levels of a plurality ofstages, based on the acquired I/O amount relating to the power controlgroup, for each of the storage devices contained in the power controlgroup, determines a designated value which corresponds to the determinedpower saving level among a plurality of designated values whichcorrespond to the storage device, based on mapping information, anddesignates this designated value for the storage device, wherein thepower saving levels of the plurality of stages are each a power savinglevel in power control group units, wherein the mapping information isinformation in which the designated value, among the plurality ofdesignated values, which corresponds to the storage device, for each ofthe two or more storage devices, is associated with each of the powersaving levels of the plurality of stages, and wherein, for each of thepower saving levels of the plurality of stages, the designated value foreach of the two or more storage devices is a value which is designatedfor the storage device to enable the storage device to demonstrate I/Operformance corresponding to the power saving level.
 3. The storagecontrol system according to claim 2, wherein, for each of the powersaving levels of the plurality of stages, the designated value for eachof the two or more storage devices depends on the number of redundancyconfiguration groups to which the storage device belongs.
 4. The storagecontrol system according to claim 1, wherein, for each of the pluralityof power control groups, when the acquired I/O amount relating to atarget power control group which is the power control group is greaterthan an I/O amount according to an I/O performance requirement whichcorresponds to a current power saving level that is associated with thetarget power control group among the power saving levels of theplurality of stages, the power control unit performs a firstdetermination which is a determination of whether or not a total powerconsumption, which is estimated in a case where a reduction in thecurrent power saving level of the target power control group is assumed,exceeds an upper limit value of the total power consumption, if theresult of the first determination is true, performs a modification toreduce the current power saving level and controls each storage devicethat belongs to the target power control group according to the modifiedpower saving level, and wherein the total power consumption is the powerconsumption for a whole entity which comprises the plurality of storagedevices.
 5. The storage control system according to claim 4, wherein thepower control unit if the result of the first determination is true,performs a second determination which is a determination of whether ornot a power control group of a lower priority than the priority of thetarget power control group exists, and if the result of the seconddetermination is false, maintains the current power saving level.
 6. Thestorage control system according to claim 4, wherein the power controlunit if the result of the first determination is true, performs a seconddetermination which is a determination of whether or not at least onepower control group of a lower priority than the priority of the targetpower control group exists, if the result of the second determination istrue, performs a third determination which is a determination of whetheror not a total power consumption, which is estimated in a case where anincrease in the current power saving level of the at least one powercontrol group and a reduction in the current power saving level of thetarget power control group are assumed, is equal to or smaller than anupper limit value of the total power consumption, if the result of thethird determination is true, performs a modification to increase thecurrent power saving level of the at least one power control group andcontrols each storage device that belongs to the at least one powercontrol group according to the modified power saving level, and performsa modification to reduce the current power saving level of the targetpower control group and controls each storage device that belongs to thetarget power control group according to the modified power saving level.7. The storage control system according to claim 1, wherein theplurality of storage devices are each storage devices which are alsocapable of transitioning to any power savings state of a plurality ofstages which are states in which the storage devices are eachI/O-capable.
 8. The storage control system according to claim 7, whereinthe plurality of storage devices are each NVRAM (Non-Volatile RAM).
 9. Apower consumption control method, comprising: acquiring, for each of aplurality of power control groups in which a plurality of storagedevices which form the basis of a plurality of redundancy configurationgroups are classified, an I/O (Input/Output) amount of the power controlgroup, the plurality of redundancy configuration groups all being astorage device group which stores redundant data, and none of theplurality of redundancy configuration groups spanning two or more powercontrol groups among the plurality of power control groups, all beingcontained in any of the plurality of power control groups; andcontrolling, for each of the plurality of power control groups, thepower consumption of each of the storage devices belonging to the powercontrol group in power control group units, based on the acquired I/Oamount relating to the power control group.
 10. A computer program forcausing a computer to: acquire, for each of a plurality of power controlgroups in which a plurality of storage devices which form the basis of aplurality of redundancy configuration groups are classified, an I/O(Input/Output) amount of the power control group, the plurality ofredundancy configuration groups all being a storage device group whichstores redundant data, and none of the plurality of redundancyconfiguration groups spanning two or more power control groups among theplurality of power control groups, all being contained in any of theplurality of power control groups; and control, for each of theplurality of power control groups, the power consumption of each of thestorage devices belonging to the power control group in power controlgroup units, based on the acquired I/O amount relating to the powercontrol group.